The present invention generally relates to valves and more particularly relates to electromagnetic valves controlling fluid flow.
DE 196 21 229 A1 discloses electromagnetic valves, each comprised of a housing base member for attachment in a valve accommodating member, with a valve sleeve in which a magnetic armature is guided projecting from the housing base member of each electromagnetic valve. Interacting with the magnetic armature in each case is a tappet which has a valve closure member that faces a valve seat member. Further, one valve coil which, among others, is passed through the valve sleeve is disposed on each housing base member. To produce the magnetic circuit necessary for operation of the electromagnetic valves, a yoke ring encompassing the valve coil contacts in an axial direction of the valves a block-shaped valve accommodating member as well as the sleeve or magnetic core area of the respective electromagnetic valve which is remote therefrom.
However, the described valve assembly suffers from the disadvantage that the magnetic circuit is closed only when the valve accommodating member is composed of a material that conducts the magnetic flow. Another shortcoming is that when a non-magnetic valve sleeve is used, the inside contour of the yoke ring must be overturned correspondingly deeply at the radial contact surface relative to the valve sleeve in order to minimize magnetic losses. Still another shortcoming is that for discharging the heat generated by the valve coil there is only a very small contact area between the yoke ring and the valve accommodating member that acts as a heat sink. Further, special measures are required in individual cases for the exact valve stroke adjustment or air gap adjustment which previously necessitated maintaining minimum possible fit or manufacturing tolerances for fixing the tappet on the magnetic armature.
U.S. Pat. No. 5,460,437 describes an electromagnetic valve which is open in its initial position and the tappet of which is directly supported on a front surface of the magnetic armature. Consequently, the position of the tappet depends on the manufacturing tolerances of valve parts that correspond with each other and, especially, on the assembly tolerances of the valve seat in the housing base member and the valve sleeve slipped upon the housing base member. In the design of the electromagnetic valve being closed in its initial position, the tappet is arranged in the magnetic armature so that the attachment of the tappet is influenced by manufacturing tolerances as well as by assembly tolerances.
An object of the present invention is to eliminate the disadvantages of the above-mentioned state of the art and to provide an electromagnetic valve which is distinguished by a particularly simple manufacture, especially by a tappet adjustment which is as independent as possible from fit tolerances, and permits universal modification in its way of functioning by simple means, if required.